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crowding root systems for dwarfing effect

Posted by Todd Parlo 
crowding root systems for dwarfing effect
February 23, 2013 08:28PM
I wanted to bring attention to a study we are doing at Walden Heights. In both research and direct observation, there is evidence that crowding of root systems leads to some dwarfing effects. Apples in particular tend to avoid growing in the same soil regions that other members of their species do. ( Atkinson D, Naylor D, Coldrick GA (1976) The effect of tree spacing on the apple root system. Hortic Res 16: 89-105 ). Additional consideration is that direct competition of many other species in the vicinity should lead to an overall size reduction. By creating a full block planting, roots will be forced to compete 360 degrees.

We have planted two sections to standard stock apple, one as an 8x8 foot grid, one as an 4x8 foot grid. We also, for comparison have standards at 15 x 15, and 30 x 30. We also have apples (part of another test) in a high tunnel at 8 foot spacing. Our collection of scionwood for the nursery currently takes precedent over crop consideration, so for us if the fruit production is, well, unfruitful, there is still merit in the exercise. We are forced by necessity since we need to find room for what is closing in on 500 varieties, without resorting to dwarf stock or excessive topworking. It gives us an opportunity to run such a test without risking too much. We will keep everyone posted on the progress. There are about 500 trees in the two blocks, of 6 standard rootstocks and roughly 300 scion varieties.

Obviously precocity isn't necessarily being addressed, at least at first glance. Since stress often leads to early bearing, who knows. If excessive pruning is needed in the early years, this may actually delay bearing. Our goals here have never been for rushing the crop- thats what berry bushes are for. Tree longevity and low maintenance plants are. If we can couple this with a tree that can more within reach for spraying, harvesting and scion collection, it may have a place in many a farm plan. Not as a replacement, but as an addition to the whole.

Walden Heights Nursery & Orchard
Zone 3 in Vermont



Edited 2 time(s). Last edit at 02/24/2013 02:03AM by Todd Parlo.
Re: crowding root systems for dwarfing effect
March 03, 2017 10:12PM
Todd, I was wondering about this very question, what effect planting standard size trees close together would have, and found your post from 4 years ago. Do you have an update you could share about how it has worked out for you? Thanks!

Northern Wisconsin
Zone 3b
Re: crowding root systems for dwarfing effect
March 06, 2017 01:53PM
Two growers at our recent Berkshire meeting shared plans to space MM.111 and B.118 at five feet respectively. Wowser! The idea being to establish a well-rooted "trellis" without actually needing posts and wires. This is going to take considerable branch bending and rigid adherence to diameter-based pruning to maintain. But it's cool that both Steve at South Hill Cider and Eric at Redbyrd Cider want to give this a shot. No need to eliminate sod competition coupled with a stout leader capable of holding up its own may turn out to be quite cost-effective. Trees in both cases are going in the ground this spring in central New York. The further North you go with an idea like this, the better I think, just because unrestrained vigor in a long growing season could get old fast.

Lost Nation Orchard
Zone 4b in New Hampshire
Re: crowding root systems for dwarfing effect
March 06, 2017 06:03PM
So glad this thread was revived. I, too, am very curious to hear how your trial is doing, Todd. Another thought - has anyone trying this incorporated intentional understory plantings (whether herbs, appropriate region specific natives, strawberries, etc.) to try to curb vigor beyond not bothering to suppress what pops up unintentionally?

Door Creek Orchard
Zone 5a in Wisconsin
Re: crowding root systems for dwarfing effect
March 06, 2017 06:40PM
By managing for understory plants that provide specific ecosystem services (e.g., pollinators, nutrient accumulators, pest deterrents, etc) to the orchard ecosystem within the tree row and between the rows, I would hope to achieve a wide range of benefits including reducing tree vigor (i.e., calming the tree) and increasing orchard resiliency. There are wide range of plants that will come in on their own - some are beneficial, others I would define as noxious - and others that need to be purposefully planted. Once the orchard understory reaches a desired steady state level - a dynamic equilibrium - then theoretically it should be self-regulating, getting closer to Fukuoka's "do nothing" philosophy. In terms of specifics, that is being worked out as I write this. This is something i have been working on for a while and should have something - at least from my perspective - here in a while..

Mike Biltonen, Know Your Roots
Zone 5b in New York
Re: crowding root systems for dwarfing effect
March 06, 2017 07:01PM
Right, Mike - our understory plants have the potential to provide so much! Glad to hear you are close to having something to share with us. Thank you for your work.

Door Creek Orchard
Zone 5a in Wisconsin
Re: crowding root systems for dwarfing effect
March 08, 2017 01:26AM
We have a few weird things going on up here. There is a section of trees at 4 x 4 spacing, 8 x 8 spacing, and also a greenhouse with trees at 8 x 4. Indeed this is testing, not a suggested protocol. Results ? There certainly is some taxing of the closest spaced trees, some remarkably so, but many in the "wider" spacings appear of typical vigor. The case with the latter is likely to change as they compete more. In unearthing trees over the years, I have seen apple roots avoiding their neighbors. Additionally, rootstocks often remain more confined at closer spacings. Not all species are similar in this respect. Michael is correct in assuming tight spacing would be a disaster in warmer, humid locals. Our greenhouse for instance, is an exercise in madness, though it is manageable, far more manageable than I thought, in fact. There is probably a way, if techniques are stacked (ie crowding, plus spreading, root pruning, scoring, summer pruning), to make a close planting with vigorous stock, but it wouldn't make sense without a reason. That is, if it is going to hit 40 below, there is little choice regarding rootstock, so experimentation is warranted.


There is plenty of evidence that apple root systems will detour from the vicinity of a host of plants, including their own species. In many cases (for instance, maize), they may simply dive into the lower strata. It stands to reason that there is a threshold at which the system will suffer some, resulting in slower growth. The hope, however, is that it means an even reduction in overall size or rate of growth, not an unhealthy taxing of the plant as a whole. One phenomenon is a reduction in root mass and rate of growth due to shading (as we would fine in a crowded system). Foliar shading leads to reduced canopy, and in turn roots, in a positive feedback loop. Some studies in Vt in the early 1900s showed root growth of several tree species nearly 100 percent smaller in shaded areas than in sunnier locations. Whether beneficial growth reduction through shading outweighs lower production from the same shading is debatable.

Since the high density option for most growers has really to do with ease of access to the plants and fruit (setting aside yield and precocity for the moment), an orchard in a cold location has another option. Wider spacing of vigorous trees can be treated as multiple plants. Similar to v trellis, but multiplied, vigor can be split (as in a candelabra form). Again, since the system is far more complicated and intelligent pruning and training is necessary, it is best reserved for the coldest areas, or for those that have other reasons (longevity and aesthetics for instance). If there is success, a small planting could be made in a rough climate and be physically in reach of those who may have a hard time managing large trees, particularly the elderly.

What I will end with is that the high density system only makes sense as an ecosystem if the blocks are rather small, as in a single row. I wouldn't dream of a high density system here as an end goal in a solid block, no matter how many bunches of comfrey and yarrow I shoved into the mess. Acts like this are less a plan, and more of an apology. If holistic is a nod to a whole system, that system ideally would be very dynamic. We could probably open a discussion like this in another thread.
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